Process of treating films



w. R. WEBB, I PROCESS OF TREATING FILMS.

APPLICATION FILED NOV- 4 192].

1,429, 179, PatentedSept. 12, 192".

WITNESS v W INVENTO;

W ZZZi R. 7 fifi,

ATTORNEY Patented Sept. 12,1922.

WILnIAm R. WEBB, or aocH'Es'rEa, NEW roan, assrenoa TO EAST AN KODAK com- PANY, or aocnEsrEE, NEW YORK, A CORPORATION or NEW YORK. i

I PROG'ESS OF TREATING FILMS.

Application filed November 4, 1921. Serial No. 513,647.

To all whom it may concern:

Be it known that I, WILLIAM R. WEBB,

a citizen of the United States of America,-

residing at Rochester, in the county of Monroe and State of New York, have invented certain new, and useful Improvements in Processes of Treating Films, of which the following is a full, clear, and exact specification.

This invention relates to a process of treating film, particularly film containing cellulose ethers. One object of this invention is to provide a simple, inexpensive, commercially practical method of treating such film'to lessen the tendency thereof to curl. Other objects will hereinafter appear.

In the accompanying drawing the single figure is a diagrammatic side elevation, partly in section and on a reduced scale, of a typical film-making apparatus in which my novel process may be carried out, certain parts being shown in exaggerated relative size for the sake of clearness.

It has been found that films containing cellulose ethers, such for instance as Waterinsoluble ethyl celluloses, have a tendency to curl. This tendency manifests itself to some extent in a plain filin of cellulose ether composition, but also occurs to an undesirable extent. in film which has beenscoated with a sensitive photographic emulsion Moreover, it appears also after such sensitized film, has been printed, fluid treated and dried in the usual manner. This curl may manifest itself in the case of a motion picture film strip by a tendency to curve laterally, the curl some times involving kinks and longitudinal buckling. Since this even when present in a small degree, considerabl detracts from the usefulness of the film, it is highly desirable that it be lessened or prevented, particularly in the case of film manufactured in the usual filmmaking apparatus.

I have discovered that this tendency to curl may be greatl lessened and in many cases eliminated by applyin to a face of the film a solvent thereof, t e application or treatment with the solvent being stopped before the body of the film is attacked. This may be accomplished by employing an amount of the solvent which is insufiicient to operate on more than the surface of the film; or a large amount of solvent may be used but removed before the body of the film is attacked. In the preferred form of my invention I use both a restricted amount of solvent and rapidly remove all or the greater part of it from the treated 'face of the film. This is most easily accomplished by applying a volatile solvent to the face of the film an rapidly evaporating it.

The solvents employed may be either strong solvents or they may be comparatively weak ones. Furthermore, mixtures of solvents with non-solvent diluents can be employed and various mixtures of solvents or mixtures ofstrong and weak solvents can be utilized. For a given treatment or conditioning operation, the stronger the solventemployed the less will be the amount applied to the face of the film, or the time of action will be shortened, or both lessening of the amount and shortening of the time may be employed. Typical solvents which are found advantageous are methyl alcohol, ethyl alcohol, benzyl alcohol, acetone, amyl acetate and mixtures of benzol and ethyl alcohol. These arementioned merely as typical liquids that may be employed, many other solvents being well known to those skilled in the art.

' While the fluid used is primarily one which has at least a slight solvent action on the cellulose ether, nevertheless it is no disadvantage if it likewise has some solvent power with respect to the softening or high boiling ingredients which may be present in the cellulose ether composition out of which the film is made.

Since it is particularly important that the curl be lessened in film that is made on standard apparatus, I will describe an illustrative embodiment ofmy invention in connection therewith. In the drawing, the base 1 supports a bearing} for the shaft 3 of a ,wheel or drum 4. he cylindrical peripheral facing 5 of the wheel moves during rotation in thedirection of arrow 41 from a dope-applying station 6 to a film stripping or removing station 7 and then back to station 6 past a cleaning station.

At the dope-applying station is a V-shaped trough 61 having the usual adjustable gate 62 for regulating the thickness of the layer 'of composition or coating that is deposited on facing 5. The film being drawn under tension away from the wheel 4, as indicated by arrow 71, passes over roller 72. The c eaning pad orroll 8 is carried in a swinging support 81 that is depressed toward wheel at by a spring pressed plunger 82. All of these details are Well known in the art and further explanation is, therefore, un-

necessary.

As the film becomes set or hardened on the wheel, the condition which causes curling is created in the film. If the setting of the film takes place sufficiently rapidly on the wheel, I may locate on the base 1 a shelf 92 on which is a container 91 carrying the solvent 9 which is applied to the face of the film opposite the wheel by a roller 93. Any suitable form of mechanism for applying the right amount of solvent to the film may, of course, be employed. While wicks, belts, sprays, absorbent rollers and the like may be employed, I prefer to use simply driven smooth metal rolls. If the setting or ourin of the film on the wheel does not bring it to the proper hardness for treatment While on the wheel, the application of the solvent may take place later, the container 91 and applying roll93 being then located for example in the position diagram-- 'matically indicated at the upper right hand part of the figure. Even when the film hardens rapidly enough on the wheel to permit of a solvent applying station on the base, as shown at the bottom of the figure, I may, nevertheless, use a supplementary applying station later on in the movement of the film, as indicated in the upper right hand part of the figure, the two sequential treatments being co-operative. I

While I do not wish to be confined to any particular theory, it seems probable that during the setting, hardening and final drying or curing of the film certain stresses the front face.

are set up unequally in the film and par ticularly near the face of the film which always remains out of contact with the support,that is, the wheel. This face may,

even after the film has left the wheel, be

referred to as the one that remains out of contact with the support. It is also convenient to some times refer to this face as the rear one, the face which contacted with the support wheel being conversely It seems probable that the treatment or conditioning of this face with the solvent eliminates or greatly lessens these curl-forming stresses. Generally there is no removing of the face but the solvent merely penetrates the film at the surface being treated. llt does not attack in any way the body of the film back of such surface or outer layer. The solvents of higher boiling (point, like amyl acetate, may remain in very small amounts in the treated surface layer, but when methyl alco perature, etc, by which the removal of vole inseam tile solvents is facilitated, my novel step of applying the solvent to the face of the film may conveniently take place just prior to or during such curing operation. Of course, the tendency to curl maybe lessened even if the step of applying the solvent to the proper face is performed on the film after it has been cured and stored for some time. ll prefer, however, to progressively apply the solvent to the rear face of the moving film during its movement in progressive manufacture.

Having thus described my invention, what ll claim as new and desire to secure by Letters Patentis:

l. The process of treating a film containing cellulose ether to lessen the curling tendencythereof, which comprises the steps of applying a solvent thereof to a face of .suchfilm and stopping said application bethe body of said film is attacked.

l. The recess of treating a film containing cellulose ether to lessen the curling tendency thereof, which comprises the steps of applyin a volatile solvent thereof to a face of sai film and'evaporating said applied solvent.

5. The process of lessening the tendency to curl of a film containing cellulose ether, which comprises the steps of moistening a face of said film with an amount of a volatile solvent thereof which will not attack the body of said film and rapidly evaporating said solvent.

6. ln the process of spreading a cellulose ether com osition on a support to form a film with its front face, in contact with said support, and stripping said film from said support, the step of acting on the rear face of said film with a solvent thereof and stopping said action before the body of the lm is attacked, whereby the curling tendency of the film is lessened.

7. The process of lessening the tendency to curl in film formed by spreading a cellulose ether composition on a support, stripping the film therefrom and curing 1t, which comprises the step of applying to the face of said film which remains out of contact with said sup ort an amount of a solvent thereof insu cient to attack the body of said film.

8. The process of lessening the tendency lllll to curl in film formed by spreading a cellulose ether composition on a support, strip-' ping the fihn therefrom and curlng 1t, which comprises the step of applying a solvent thereof to the face of said film which remains out of contact with said support and removing said solvent from said face before the body of said film is attacked.

9. The process of lessening the tendency to curl in film formed by spreading a V cellulose ether composition on a support,

stripping the film therefrom and curing it, which comprises the step of applying I a volatile solvent thereofto the face of said" fihn which remains outfofcontact with the support and evaporating said solvent.

10. The process of lessening the tendency to curl in film formed by spreading a cellulose ether composition on a support, stripping the film therefrom and curing it, which comprises the step of moistening the face of said film which remains out of contact with said support with an amount of a volatile solvent thereof which will not attack the body of said film and rapidly evaporating said applied solvent.

11. The process of progressively forming a moving film of cellulose ether composition, said film having a tendency to curl and progressively acting on one face of said moving fihn with a solvent thereof to lessen said tendency.

Signed at Rochester, New York, this 29th day of October 1921. 3

WILLIAM R. WEBB. 

